Vacuum stripping

ABSTRACT

Cup-shaped metal object is stripped from ram of hydraulic press using a stripper plate at end of stroke of the ram, the stripping being accomplished by applying a positive pressure inside the ram and cup-shaped object and a vacuum or substantial negative pressure outside the bottom of the object at the stripper plate.

United States Patent [72] inventor John M- llflg [56] References CitedUNITED STATES PATENTS [21] P 786046 2,990,581 7/1961 ROW6,.I!' 264/89[22] Filed Dec. 23, 1968 1 3,338,997 8/1967 Tigner 18/19 F {451 PatentedAug. 3, 1971 7 6 96 G l 29 27 [73] Assignee Aluminum Company of AmericaH 4 tamer et a M X Hush h Pa 3,266,451 8/1966 Kraus 113/120 3,270,5449/1966 Maeder et a1 113/120 3,402,591 9/1968 Maeder 72/345 PrimaryExaminerRichard J. Herbst Attorney-Abram W. Hatcher [54] VACUUMSTRIPPING 6 Chums 4 Drawing Figs ABSTRACT: C up-shaped metal object isstripped from ram of [52] [1.8. CI 72/344, hydraulic press using astripper plate at end of stroke of the 1 13/120 ram, the stripping beingaccomplished by applying a positive [51] Int. Cl B2ld 45/00 pressureinside the ram and cup-shaped object and a vacuum [50] Field of Search72/344- or substantial negative pressure outside the bottom of the ob-346; 113/120 H; 29/427, 421 ject at the stripper plate.

I0 [4 24 26 v -/s /////L//////// A V 1 ll// 20 [8 ATENIEU Am: 3197:

IN VEN TOR.

8 JOHN M. HAGAN mow M m Attorney VACUUM STRIPPING BACKGROUND OF THEINVENTION This invention relates to metal forming. More particularly, itrelates to method and apparatus for stripping a can or canister from theram or metalworking punch used in forming it.

Conventionally a metalworking punch or ram, for example, one operated bya hydraulic press, is stripped at the end of its drawing or ironingstroke from the object which it forms, for example, a cylinder, can orcup of aluminum (including aluminum-base alloys) or the like open at thetop, by a mechanical stripping device or by applying pressure inside thepunch or ram and object being formed while at the same time employing amechanical stripper. However, problems have been encountered in usingsuch stripping devices, especially when the thin-walled cans orcanisters are being formed. For instance, it is sometimes difficult toposition a mechanical stripper so that it will engage the open end ofthe can, particularly without damaging the end the can. Furthermore,pressure applied internally tends to distort the shape of the can orexpand the can beyond allowable diameter tolerances. Therefore,development of a method and apparatus which would substantially avoidsuch distortion of the cans or other objects formed by drawing orironing of a metal such as aluminum, including its alloys, represents ahighly desireable result.

SUMMARY OF THE INVENTION It is accordingly one object of lthis inventionto provide an improved method of stripping an object formed by thestroke of a metalworking punch from the punch. It is a further object toprovide an apparatus for minimizing distortion of a can or cup likeobject when stripped from a ram used in forming same by drawing andironing or the like. Other objects will be apparent from the descriptionand claims which follow.

In its broader aspects my invention involves applying a positive airpressure inside a metalworking punch or ram and a vacuum or substantialnegative-piessure on the outside at the end or bottom of the objectbeing formed, such as a cup, can or canister, that is, on the outside atthe point where the stroke of the punch or ram ends. This strips the canfrom the punch. The application of the vacuum or substantial negativepressure on the outside permits the positive pressure on the inside tobe reduced to a level which will not distort the object being formed. Aconventional hydraulic ironing press may be used to advance and retractthe punch, The substantial vacuum on the outside may be applied throughan orifice in a stripper plate positioned at the end of the stroke ofthe punch, with a pressure seal being obtained by means of an O-ring, orthe like. TheO-ring or like means may be so positioned that thesubstantial vacuum is confined to an area of maximum circumference ofabout the circumference of the closed end or bottom of the cup or can,Thus the pressure outside the side wall of the cup or can, usuallysubstantially atmospheric or room pressure, is not affected and anytendency of the pressure applied to the inside of the cup or can duringstripping to push the sidewall out of shape is thereby minimized.

BRIEF DESCRIPTION OF THE DRAWING A better understanding of my inventionmay be obtained from an examination of the drawing in which:

FIG. 1 is a schematic representation, in part broken away, depicting theram in a retracted position and shallow cylinder 12 in a load positionprior to ironing through a die 14 and against a stripper plate 16.

FIG. ,2, likewise broken away in part, shows the cylinder (without atop) 12 ironed and sealed against the stripper plate 16 by the ram 10.

FIG. 3 in a similarmanner, depicts the first part of the strippingstepin which a substantial vacuum has been applied outside the bottom ofthe cylinder 12 by vacuum applying means (such as a vacuum pump) 18 vialine 30 which passes through an orifice in stripper plate 16 and apositive pressure inside the hollow ram 10 and cylinder 12 by a positivepressure-applying means (such as a mill air line) 22 via line 2d, theram 10 has been partly retracted and the cylinder 12 is stillin contactwith the stripper plate 16.

FIG. 4 shows the second part of the stripping step with the ram 10 nowin a fully retracted position and the cylinder 12 completely strippedfrom the stripper plate and in an unload position, the O-ring gasket 26seal having been broken.

A hydraulic press or other mechanism for operating the ram is notdepicted as it may be any appropriate conventional system. Means forapplying the positive pressure and the vacuum or substantial negativepressure may also be of conventional construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT The following example isillustrative of the invention.

The steps depicted in FIGS. 1 through 4 of the drawing as describedhereinabove were employed repetitively to produce by ironingsubstantially cylindrical-shaped cans having walls about 0.0l0-inchthick and bottoms about 0.030-inch thick and subsequently 200 similarcans with walls about 0.030-inch thick and bottoms about 0.060-inchthick. Stripping of each can from ram and stripper plate wasaccomplished by applying a positive air pressure (about 25 p.s.i.g.)inside the ironing punch and a vacuum or substantial negative pressure(about --l4.7 p.s.i.g.) on the outside of the end of the can. Uniformityof dimensions of the cans was satisfactory according to commercialstandards, and the outside surface finishes were substantially unmarred.A SO-ton hydraulic ironing press was used. A vacuum pump was used toobtain the vacuum or substantial negative pressure and a mill air lineto obtain the positive pressure.

From the foregoing description and example it is apparent that thepresent invention provides means for stripping a canister from ametalworking punch without the use of mechanical devices which mightdistort, scratch, or otherwise damage the canister. A further advantageof the invention is that the terminal stripper plate may be made movableto an unloading station, for example, by use of a vacuum system in whichit serves as a vacuum transfer head, thus additionally minimizing thepossibility of damage to the can or cup-shaped object being strippedfrom the punch, ram, or plunger.

While the invention has been described in terms of preferredembodiments, the claims appended hereto are intended to encompass allembodiments which fall within the spirit of the invention.

Having thus described my invention and certain embodiments thereof, Iclaim: I

1. A process for stripping a closed end metal object from a metalworkingpunch and a stripper plate which comprises applying a vacuum orsubstantial negative gauge pressure outside the end of the object andthe stripper plate and a positive gauge pressure inside the punch,holding the end of the object against the plate and withdrawing thepunch while the end of the object is so held, thereby effecting thestripping of the object from the punch and stripper plate.

2. The process of claim I wherein the metal object is an aluminum canand the vacuum or substantial negative gauge pressure applied outsidethe object is applied in the vicinity of the closed end of the canthrough an orifice in the stripper plate substantially against which theobject rests prior to the stripping.

3. The process of claim 2 wherein the vacuum or substantial negativepressure applied outside the aluminum can in the vicinity of the closedend is restricted to a maximum area about the size of the closed end ofthe can by means of a seal, thereby substantially preventing distortionof the remainder of said can other than said closed end.

4. Apparatus for stripping a closed end metal object from a punchcomprising in combination a hollow metalworking punch axially alignedwith a metal workpiece adapted to be formed into said closed end metalobject, means for forcing said punch against said workpiece to form itinto said closed end metal object, means for retracting said punch fromagainst said workpiece formed into said closed end metal object,cooperative means for applying a positive gauge pressure to the insideof said punch and for applying a vacuum or substantial negative gaugepressure outside said punch in the vicinity of the closed end of saidmetal object, whereby said closed end of said metal object is heldagainst a stripper plate and stripped from said punch and stripper plateafter having been formed into said closed end metal object.

5. The apparatus of claim 5 wherein a terminal plate is axican having anannular sidewall joined to said closed end and wherein an O-ring isprovided on the surface of said terminal plate next to said punch andsaid O-ring is of substantially the same diameter as that of the closedend of said can, said O- ring being adapted to seal against said closedend of said can.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,596,494 Dated August 3 197].

Inventor(s) John M. Hagan It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Col. 1, line 19 Delete "the" after "when".

Col. 1, line 28 Change "desireable" to -desirable--.

Claim 5, line 13 Change "5" to --4-.

Claim 5 line 4 After "negative" insert --gauge--.

Signed and sealed this 25th day of January 1972.

( SEAL) Attest:

EDWARD M.FLJ:.'TCHER,JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents USCOMM-DC 60376-P69 FORM PO-1050 {10-69) UsGOVERNMENT wmmms orncr I969 o-aea'sal

1. A process for stripping a closed end metal object from a metalworkingpunch and a stripper plate which comprises applying a vacuum orsubstantial negative gauge pressure outside the end of the object andthe stripper plate and a positive gauge pressure inside the punch,holding the end of the object against the plate and withdrawing thepunch while the end of the object is so held, thereby effecting thestripping of the object from the punch and stripper pLate.
 2. Theprocess of claim 1 wherein the metal object is an aluminum can and thevacuum or substantial negative gauge pressure applied outside the objectis applied in the vicinity of the closed end of the can through anorifice in the stripper plate substantially against which the objectrests prior to the stripping.
 3. The process of claim 2 wherein thevacuum or substantial negative pressure applied outside the aluminum canin the vicinity of the closed end is restricted to a maximum area aboutthe size of the closed end of the can by means of a seal, therebysubstantially preventing distortion of the remainder of said can otherthan said closed end.
 4. Apparatus for stripping a closed end metalobject from a punch comprising in combination a hollow metalworkingpunch axially aligned with a metal workpiece adapted to be formed intosaid closed end metal object, means for forcing said punch against saidworkpiece to form it into said closed end metal object, means forretracting said punch from against said workpiece formed into saidclosed end metal object, cooperative means for applying a positive gaugepressure to the inside of said punch and for applying a vacuum orsubstantial negative gauge pressure outside said punch in the vicinityof the closed end of said metal object, whereby said closed end of saidmetal object is held against a stripper plate and stripped from saidpunch and stripper plate after having been formed into said closed endmetal object.
 5. The apparatus of claim 5 wherein a terminal plate isaxially aligned with said punch on the opposite side of said workpiecefrom said punch and an orifice is provided in said terminal plate, saidorifice being connected to said means for applying said vacuum orsubstantial negative pressure.
 6. The apparatus of claim 5 wherein theclosed end metal object is a substantially cylindrical-shaped open-topaluminum can having an annular sidewall joined to said closed end andwherein an O-ring is provided on the surface of said terminal plate nextto said punch and said O-ring is of substantially the same diameter asthat of the closed end of said can, said O-ring being adapted to sealagainst said closed end of said can.